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Подготовка к TOEFL:Чтение/Set 1. Avalanches
}}} An avalanche is a rapid flow of snow down a slope. Typically avalanches occurr in mountainous terrain, being triggered by either human activity or natural processes. Powerful avalanches have the capability to entrain ice, rocks, trees, and other material on the slope; however avalanches are always initiated in snow, are primarily composed of flowing snow, and are distinct from mudslides, rock slides, rock avalanches, and serac collapses from an icefall. In mountainous terrain avalanches are among the most serious objective hazards to life and property, with their destructive capability resulting from their potential to carry an enormous mass of snow rapidly over large distances. For example, one of the most notable avalanches that took place in France in 1999 resulted in 15 deaths. It literally buried people in their chalets under 5 meters thick layer of snow. What differs avalaches from other disasters, such as hurricane or earthquake is that avalanches are almost unpredictable. That’s why prevention is especially important in areas where avalanches pose a significant threat to people. Examples are ski resorts, mountain towns, roads and railways. There are several ways to prevent avalanches and lessen their power and destruction. They can be divided in three main categories. The first one includes various means that direct the placement of snow, such as snow fences and light walls. Snow builds up around the fence, especially the side that faces the prevailing winds. Downwind of the fence, snow buildup is lessened. This is caused by the loss of snow at the fence that would have been deposited and the pickup of the snow that is already there by the wind, which was depleted of snow at the fence. When there is a sufficient density of trees, they can greatly reduce the strength of avalanches. They hold snow in place and when there is an avalanche, the impact of the snow against the trees slows it down. Trees can either be planted or they can be conserved, such as in the building of a ski resort, to reduce the strength of avalanches. The second and very broad one includes artificial barriers. One kind of barrier (snow net) uses a net strung between poles that are anchored by guy wires in addition to their foundations. These barriers are similar to those used for rockslides. Another type of barrier is a rigid fence like structure (snow fence) and may be constructed of steel, wood or pre-stressed concrete. They usually have gaps between the beams and are built perpendicular to the slope, with reinforcing beams on the downhill side. Rigid barriers are often considered unsightly, especially when many rows must be built. They are also expensive and vulnerable to damage from falling rocks in the warmer months. Finally, there are barriers that stop or deflect avalanches with their weight and strength. These barriers are made out of concrete, rocks or earth. They are usually placed right above the structure, road or railway that they are trying to protect, although they can also be used to channel avalanches into other barriers. Occasionally, earth mounds are placed in the avalanche’s path to slow it down. These methods are often impractical in some areas, especially at ski resorts. In this case explosives are used extensively to prevent avalanches. Explosive charges are used to trigger small avalanches before enough snow can build up to cause a large avalanche. }}} {What makes avalanche so dangerous according to paragraph 1? |type="()"} - Rocks and other large objects that they carry + Enormous mass along with high velocity - Enormous mass - They often occur suddently {According to passage, which of the following methods are not used to prevent avalanches? |type="()"} -Artificial triggers - Barriers - Snow walls + Precpitation control {What does the word «enormous' in the paragraph 2 mean? |type="()"} - Outstanding - Hazardous + Very large - Uncontrollable {What does highlighted pronoun they refer to? |type="()"} - Methods + Categories - Avalanches - Dangers